The Integumentary System By WILLIAM M. BANAAG, R.N.
Integumentary System The organ system that protects the body from damage, comprising the skin and its appendages (including hair, scales, and nails), glands and nerve endings. It distinguishes, separates, protects and informs the animal with regard to its surroundings. Small-bodied invertebrates of aquatic or continually moist habitats respire using the outer layer (integument). This gas exchange system, where gases simply diffuse into and out of the interstitial fluid, is called integumentary exchange.
SKIN The skin is the outer covering of the body In humans, it is the largest organ of the integumentary system made up of multiple layers of epithelial tissues, and guards the underlying muscles, bones, ligaments and internal organs Human skin is like that of most other mammals except that it is not protected by a pelt and appears hairless though in fact nearly all human skin is covered with hair follicles
Function of SKIN Protection: an anatomical barrier from pathogens and damage between the internal and external environment in bodily defense; Sensation: contains a variety of nerve endings that react to heat and cold, touch, pressure, vibration, and tissue injury. Heat regulation: the skin contains a blood supply far greater than its requirements which allows precise control of heat loss by radiation, convection, conduction and evaporation. Dilated blood vessels increase perfusion and heat loss while constricted vessels greatly reduce blood flow in the skin and conserve heat. Aesthetics and communication: others see our skin and can assess our physical state and attractiveness. Storage and synthesis: acts as a storage center for lipids and water, as well as a means of synthesis of vitamin D (calcitriol) by action of UV on certain parts of the skin. Excretion: sweat contains urea, however its concentration is 1/130th that of urine, hence excretion by sweating is at most a secondary function to temperature regulation. Absorption: Oxygen, nitrogen and carbon dioxide can diffuse into the epidermis in small amounts, some animals use their skin for their sole respiration organ. In addition, medicine can be administered through the skin, by ointments or by means of adhesive patch. The skin is an important site of transport in many other organisms. Water resistance: The skin acts as a water resistant barrier so essential nutrients arent washed out of the body.
SKIN Anatomy EPIDERMIS – the outer thinner portion which is composed of epithelial tissue ◦ Keratinocytes – produce the protein keratin that helps waterproof and protect the skin and underlying tissues. It is the major epidermal cell. ◦ Melanocytes – produces the pigment melanin – a brown-black pigment that contributes to skin color and absorbs ultraviolet (UV) light from the sun. ◦ Langerhans cell – interacts with white blood cells called Helper-T cells in immune responses, and are easily damaged by UV radiation. ◦ Merkel cell – located on the deepest layer of epidermis (Stratum Basale). It make contact with the ending of a sensory neuron, and are thought to function in the sensation of touch.
Layers of the Epidermis Stratum Corneum ◦ consists of 25 to 30 rows of dead cells, completely filled with keratin. Cells on this layers are continuously shed and replaced by cells from deeper strata. It serves as an effective barrier against light and heat waves, bacteria and many chemicals. Stratum Lucidum ◦ usually not present on hairy skin, only the thick skin of the palm and soles has this layer. It contains intermediate substance that was formed from keratohyalin which continually transformed to keratin. Stratum Granulosum ◦ develops keratohyalin – the precursor of keratin. Stratum Spinosum ◦ tightly joins the lower and upper layer together. Stratum Basale ◦ capable of continued cells division; produces stem cells that produce and multiply melanocytes and keratinocytes, which push up toward the surface and become part of the more superficial layer.
SKIN Anatomy DERMIS – composed of connective tissue containing collagen and elastic fibers. It varies in thickness, very thick in the palms and soles, and very thin in the eye lid and other parts of the body. ◦ Fibroblasts – cell that produces collagen and elastic fibers. ◦ Macrophages – cell of the lymphatic which fights bacteria. ◦ Adipocytes – cells that make up the adepose tissue
Two Regions of the Dermis Papillary Region – the upper dermal region. It is uneven and has fingerlike projections from its superior surface called Dermal Papilae. ◦ Dermal Papilae: ◦ Indents the epidermis above ◦ Contains capillary loop which furnish nutrients to epidermis ◦ They are arranged in definite patterns on the palm of the hands and soles of the foot that form looped and whorled ridges on the surface that increase friction and enhance gripping ability of the finger and feet ◦ The pattern is genetically determined. Reticular Layer – the deepest region. ◦ It contains blood vessels, sweat and oil glands, and deep pressure receptors (Pacinian Corpuscle) Sudoriferous ◦ Contains many phagocytes that act to (sweat) glands prevent bacteria that managed to get Pacinian through the epidermis from penetrating Sebaceous (oil) Corpuscle any deeper into the body. glands ◦ Contains combination of collagen fibers that strengthens the skin, and elastic fibers that gives elasticity to the skin.
Skin Color 3 Pigments that Contributes to Skin Color are: Melanin – located mostly in the epidermis Carotene – mostly in the dermis Hemoglobin – in red blood cells within capillaries in the dermis.
Appendages of the Skin (HAIR) HAIR – composed of columns of dead, keratinized cells welded together. ◦ its primary function is protection, though limited. Hairs on the head guards the scalp from injury and the sun’s rays, it also decreases heat loss. Eyelashes protects the eyes from foreign particles Hairs in nostrils protects against inhaling insects and foreign particles.
Hair Color Due primarily to melanin in the hair cortex and medulla Dark-colored hair contains mostly true melanin Blond and red hair contain variants of melanin in which there is iron and more sulphur Graying of hair is the loss of pigment believed to be the result of a progressive decline of tyrosinase – an enzyme necessary for the production of melanin.
Appendages of the Skin (GLANDS) Sebaceous (oil) Glands – produces sebum which moistens hairs and waterproofs the skin ◦ They are usually connected to hair follicles and they are absent in the palm and soles Sudoriferous (sweat) Glands – produces perspiration which carries small amount of wastes to the surface and assists in maintaining body temperature. Two types of sudoriferous glands are: ◦ Apocrine Sweat Glands – are largely distributed to the skin of the axilla, pubis and areola; their ducts open into hair follicles; they begin to function at puberty and produce a more viscous secretion that eccrine sweat glands; they are stimulated during emotional stress and sexual excitement. ◦ Eccrine Sweat Glands – extensively distributed to the entire skin except for the margins of the lips, nail beds of the fingers and toes, most parts of the genitals, and eardrums; their ducts terminates at pores at the surface of the epidermis; most numerous in the palms and the soles; eccrine sweat glands function throughout life and produce a secretion that is more watery than that of apocrine sweat glands Ceruminous Glands – are modified sudoriferous glands that produce cerumen, they are found in the external auditory meatus.
Appendages of the Skin (NAIL) NAILS – are plates of tightly packed, hard, keratinized cells of the epidermis. ◦ Nail Body – is the portion of the nail that is visible ◦ Free Edge – is the part that may extend past the end of the digit ◦ Nail Root – is the portion that buried in a fold of the skin. ◦ Lunula – the whitish semilunar area of the nail.
Homeostatic Relationship Between Integumentary System and Other Body System Endocrine System: Nervous System: Skin protects endocrine organs Cutaneous sensory receptors are located in the skin Androgens produced by the endocrine system activate Nervous system regulates diameter of blood vessels sebaceous glands and help regulate hair growth; in skin; activates sweat glands, contributing to estrogen helps maintain skin hydration thermoregulation; interprets cutaneous sensation; Lymphatic System: activates arrector pili muscles. Aside from protection, it also prevents pathogen Respiratory System: invasion Skin protects the respiratory organs Lymphatic system prevents edema by picking up Respiratory system furnishes oxygen to skin cells and excessive leaked fluids; immune system protects the removes carbondioxide via gas exchange with blood skin cells Cardiovascular System: Digestive System: Aside from protecting the cardiovascular organs, skin Skin not only protects digestive organs, it also also prevents fluid loss from body surface; it also provides vitamin D needed for calcium absorption serves as blood reservoir. Digestive system provides needed nutrients for the Cardiovascular system transport oxygen and skin nutrients to skin and removes wastes from skin; it Urinary System: also provides substances needed by skin gland to make their secretions Aside from protection, skin also helps the urinary system by excreting salts and some nitrogen wastes Reproductive System: thru sweating Skin also protects reproductive organs; highly Urinary system activates vitamin D made by modified sudoriferous glands (mammary glands) keratinocytes; disposes off nitrogenous wastes of produces milk. During pregnancy, skin stretches to skin metabolism accommodate growing fetus. Muscular System: During pregnancy, changes in skin pigmentation may occur. Skin protects the muscles Skeletal System: Active muscles generate large amount of heat which increase blood flow to the skin and may promote Skin protects the bones; it also synthesizes vitamin D activation of sweat glands of skin that bones needed for normal calcium absorption and deposit of bone salts (calcium) which make bones hard Skeletal system provides support for the skin.